\begin{table}%t1
\caption{\xmm\ and \chandra~bestfit parameters (*~corresponds to a~fixed parameter).}\label{tab1}
%\centering
\small
\begin{tabular}{p{0.25\linewidth}cc}
\hline
\hline
Parameter      & \xmm  & \chandra \\
               & value & value\\
\hline
$A$ & $1.000^*$ & $1.000^*$\\
$A_{\rm Fe}$  & $1.000^*$ & $1.000^*$\\ 
$N_{\rm H}(10^{21}~{\rm cm}^{-2})$ & $\rm 4.953^{+0.0016}_{-0.0019}$ & $\rm 7.740^{+0.52}_{-0.64}$ \\
$\Gamma_1$ & $1.56^*$ & $\rm 3.7^{+0.9}_{-1.4}$\\
%& & \\[-8pt]
\hline
%& & \\[-8pt]
$\chi^2$/d.o.f. & 302/230 & 294/288\\
\hline
\end{tabular}
\end{table}